netdev - Re: [PATCH net-next] net-sysfs: display two backlog queue len separately

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Message-ID: <CAL+tcoAmWU0w5dJ6_fL9yp1sMOF3px-n=H=kqaWwosHuzvijqA@mail.gmail.com>
Date:   Mon, 13 Mar 2023 20:19:53 +0800
From:   Jason Xing <kerneljasonxing@...il.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next] net-sysfs: display two backlog queue len separately

On Mon, Mar 13, 2023 at 8:11 PM Simon Horman <simon.horman@...igine.com> wrote:
>
> On Mon, Mar 13, 2023 at 09:55:37AM +0800, Jason Xing wrote:
> > On Mon, Mar 13, 2023 at 3:02 AM Simon Horman <simon.horman@...igine.com> wrote:
> > >
> > > On Sat, Mar 11, 2023 at 11:17:56PM +0800, Jason Xing wrote:
> > > > From: Jason Xing <kernelxing@...cent.com>
> > > >
> > > > Sometimes we need to know which one of backlog queue can be exactly
> > > > long enough to cause some latency when debugging this part is needed.
> > > > Thus, we can then separate the display of both.
> > > >
> > > > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > > > ---
> > > >  net/core/net-procfs.c | 17 ++++++++++++-----
> > > >  1 file changed, 12 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
> > > > index 1ec23bf8b05c..97a304e1957a 100644
> > > > --- a/net/core/net-procfs.c
> > > > +++ b/net/core/net-procfs.c
> > > > @@ -115,10 +115,14 @@ static int dev_seq_show(struct seq_file *seq, void *v)
> > > >       return 0;
> > > >  }
> > > >
> > > > -static u32 softnet_backlog_len(struct softnet_data *sd)
> > > > +static u32 softnet_input_pkt_queue_len(struct softnet_data *sd)
> > > >  {
> > > > -     return skb_queue_len_lockless(&sd->input_pkt_queue) +
> > > > -            skb_queue_len_lockless(&sd->process_queue);
> > > > +     return skb_queue_len_lockless(&sd->input_pkt_queue);
> > > > +}
> > > > +
> > > > +static u32 softnet_process_queue_len(struct softnet_data *sd)
> > > > +{
> > > > +     return skb_queue_len_lockless(&sd->process_queue);
> > > >  }
> > > >
> > > >  static struct softnet_data *softnet_get_online(loff_t *pos)
> > > > @@ -169,12 +173,15 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
> > > >        * mapping the data a specific CPU
> > > >        */
> > > >       seq_printf(seq,
> > > > -                "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n",
> > > > +                "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x "
> > > > +                "%08x %08x\n",
> > > >                  sd->processed, sd->dropped, sd->time_squeeze, 0,
> > > >                  0, 0, 0, 0, /* was fastroute */
> > > >                  0,   /* was cpu_collision */
> > > >                  sd->received_rps, flow_limit_count,
> > > > -                softnet_backlog_len(sd), (int)seq->index);
> > > > +                0,   /* was len of two backlog queues */
> > > > +                (int)seq->index,
> > >
> > > nit: I think you could avoid this cast by using %llx as the format specifier.
> >
> > I'm not sure if I should change this format since the above line is
> > introduced in commit 7d58e6555870d ('net-sysfs: add backlog len and
> > CPU id to softnet data').
> > The seq->index here manifests which cpu it uses, so it can be
> > displayed in 'int' format. Meanwhile, using %8x to output is much
> > cleaner if the user executes 'cat /proc/net/softnet_stat'.
> >
> > What do you think about this?
>
> I think %08llx might be a good way to go.
> But perhaps I'm missing something wrt to changing user-facing output.
>
> In any case, this is more a suggestion than a request for a change.

Ah, now I see. Thanks again for your review and suggestion :)

Thanks,
Jason